The present invention relates to an image sensor, more particularly, to an apparatus for panning a particular window of a full window and for scaling a window in reading sensing data in an image sensor.
In general, an image sensor is an apparatus for capturing image by using a light sensitive characteristic of a semiconductor and consisted of from hundreds to millions of pixels, in which each unit pixel comprises a light sensitive device. The device converts a photon to an electron-hole pair to store charge. The quantity of charge depends to light strength and light illuminating time. After that, an image sensor observes the charge and converts the pixel data of light to electric data.
FIG. 1 is a block diagram of a prior CCD (charge Coupled Device) image sensor.
As shown the FIG. 1, the CCD image sensor converts the image data of light outputted from a pixel array 100 consisted of a plurality of unit pixels to electric data. Thus, the CCD image sensor cannot selectively read a particular portion of a full window because of transferring charge as such. Namely, the image sensor vertically transfers charge a unit of a row of the pixel array 100 and moves the row to an analog shift register 110. Then, the image sensor horizontally transfers the row and outputs it as a pixel data.
Accordingly, since such CCD image sensor must read all the frames in even of intending to read a particular portion of frame, it wastes a time on reading operation.
FIG. 2 is a block diagram of a prior CMOS image sensor consisted of an active pixel array.
As shown the FIG. 2, the CMOS image sensor involves a row driver 210 capable of selectively driving a row of a desired pixel array 200 and reading a pixel data via a row address generator (unshown). The pixel data of the row is transferred to a shift register 220 and is outputted as a pixel data after horizontally and serially shifted from the shift register 220.
The shift register 220 may store and shift analog pixel data or digital pixel data converted from pixel data of the row selected before the shift register 220. In the former case, it is needed to convert analog pixel data outputted from the shift register 220 to digital pixel data in the following process.
Accordingly, while the CCD image sensor like FIG. 2 can selectively a row of pixel array because of serially output of pixel data of a row read, it cannot selectively read a column of pixel array.